Air conditioner and method of controlling the same

ABSTRACT

An air conditioner includes first and second compressors, an outdoor heat exchanger through which refrigerant discharged from the first and second compressors passes, an outdoor fan for forcedly directing air toward the outdoor heat exchanger, an expansion valve for expanding the refrigerant discharged from the outdoor heat exchanger, an indoor heat exchanger through which the refrigerant expanded in the expansion valve passes, a linear expansion valve for adjust a flow rate of the refrigerant, a load detecting unit for deterring an indoor load, and a control unit for controlling the operation of the first and second compressors in accordance with the detected indoor load. In a state where the second compressor is not driven, the control unit allows the second compressor to drive when a driving start conditioner of the second compressor is satisfied and a driving start retarding time has been elapsed. The control unit adjusts an opening of the linear expansion valve and an operation of the outdoor fan for the driving start retarding time.

The present application claims priority under 25 U.S.C. 119 and 35 U.S.C. 365 to Korean Patent Application No. 10-2006-0045421 (field on May 20, 2006), which is hereby incorporated by reference in its entirety.

BACKGROUND

1. Field

This disclosure relates to an air conditioner and a controlling method thereof.

2. Description of the Related Art

Generally, an air conditioner is an electronic appliance that maintains indoor air at a most proper state in accordance with use and purpose. For example, the air conditioner allows the indoor air to be in a cool state in summer and allows the indoor air to be in a hot state in winter. Further, the air conditioner controls a humidity of the indoor space and purifies the air by removing impurities from the air.

The air conditioners are classified into split type air conditioners where indoor and outdoor units are separated from each other and integral type air conditioners where the indoor and outdoor units are integrally coupled to each other.

Meanwhile, the air conditioner includes a compressor for compressing refrigerant, an outdoor unit, an expansion valve, and an indoor heat exchanger, thereby forming one cycle. Recently, a plurality of compressors having different volumes have been used to vary the compression volume in accordance with indoor load.

That is, in the air conditioner having two compressors (first and second compressors) having different volumes, only one of the first and second compressors is used when the indoor load is relatively low and both of the first and second compressors are used when the indoor load is relatively high.

Further, when the indoor load is reduced in a state where both of the compressors are operating due to the high indoor load, one of the compressors is not driven. In this state, when the indoor load increases again, the stopped compressor is driven again. That is, both of the compressors are driven.

SUMMARY

An implementation of an air conditioner includes a plurality of compressors that are selectively driven in accordance with the indoor load.

When it is intended to driving start a stopped compressor, the stopped compressor starts operating after a predetermined driving start retarding time has been elapsed. Discharge and intake pressures of the stopped compressor are adjusted for the predetermined driving start retarding time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating an operational cycle of an air conditioner;

FIG. 2 is a block diagram illustrating a control method of an air conditioner; and

FIG. 3 is a flowchart illustrating a control method of an air conditioner.

DETAILED DESCRIPTION

FIG. 1 is a view illustrating an operational cycle of an air conditioner.

Referring to FIG. 1, an air conditioner includes compressors 12 and 14 for compressing refrigerant an outdoor heat exchanger 30 for condensing the refrigerant compressed in the compressors 12 and 14, an expansion valve 50 for expanding the refrigerant condensed in the outdoor heat exchanger 30, and an indoor heat exchanger 60 for converting the refrigerant expanded by the expansion valve 50 into gas-phased refrigerant.

An outdoor fan 32 is provided at the outdoor heat exchanger 30 and an indoor fan 62 is provided at the indoor heat exchanger 60.

In addition, a linear expansion valve 40 is provided at an outlet side of the outdoor heat exchanger 30.

In more detail, the compressors 12 and 14 are selectively operated to vary the capacity of the air conditioner in accordance with the indoor load. The compressors 12 and 14 will be respectively referred to as first and second compressors.

Here, the first compressor 12 may be an inverter compressor whose capacity is variable. The second compressor 14 may be a constant compressor that operates constantly.

Therefore, when the indoor load is relatively low, only the first compressor 12 is driven. Subsequently, when the indoor load increases to be higher than the capacity of the first compressor 12, the second compressor 14 is additionally driven. Alternatively, when the indoor load is relatively low, only the second compressor 14 is driven. Subsequently, when the indoor load increases to be higher than the capacity of the second compressor 14, the first compressor 12 may be additionally driven.

In the present embodiment, a case where the first compressor 12 is firstly driven and subsequently the second compressor 14 is additionally driven in accordance with the indoor load.

With the above structure of the air conditioner, when the air conditioner operates with a cooling mode, the refrigerant discharged from the indoor heat exchanger 60 is directed into the compressors 12 and 14 and compressed therein. The refrigerant compressed in the compressors 12 and 14 flows inside of the outdoor heat exchange 30 to heat-exchange with an external air.

The refrigerant passing through the outdoor heat exchanger 30 is pressure-reduced while passing through the expansion valve 50. At this point, an amount of the refrigerant directed to the expansion valve 50 varies in accordance with an opening of the linear expansion valve 40.

The refrigerant that is pressure-reduced while passing through the expansion valve 50 heat-exchanges with indoor air while passing through the indoor heat exchanger 60. The indoor heat exchanger 60 passing through the indoor heat exchanger 60 is directed to the compressors 12 and 14 again, thereby completing a cooling cycle of the air conditioner.

The indoor load may vary during the operation of the air conditioner. When the indoor load is relatively low, only the first compressor 12 operates.

In a state where only the first compressor 12 operates, when the indoor load increases to be higher than the capacity of the first compressor 12, the operation of the second compressor 14 is required.

At this point, the second compressor 14 starts operating after an driving start retarding time, e.g., 10 minutes, has been elapsed from the stopping of the operation.

That is, in order to prevent the operation failure of the second compressor 14, the second compressor starts operating after a difference between an intake pressure and a discharge pressure of the second compressor is less than a predetermined value.

Here, when the driving start of the second compressor 14 is required before the driving start retarding time has been elapsed from the stopping state, the second compressor 14 starts operating after the driving start retarding time has been elapsed. When the driving start of the second compressor 14 is required after the driving start retarding time has been elapsed from the stopping state, the second compressor 14 immediately starts operating.

However, even when there is the driving start retarding time, the difference between the discharge pressure and the intake pressure of the second compressor is not less than a predetermined value, e.g., 0.2 bar, there may be a driving start failure of the second compressor.

Therefore, in order to prevent the driving start failure of the second compressor, it is preferable that the difference between the exhaust and intake pressures is forcedly reduced to be less than the predetermined value before the driving start retarding time has been elapsed.

The following will describe a method for preventing the driving start failure of the second compressor 14 in more detail.

FIG. 2 is a block diagram illustrating a control method of an air conditioner according to an embodiment of the present invention, and FIG. 3 is a flowchart illustrating a control method of an air conditioner according to an embodiment of the present invention.

Referring to FIG. 3, the air conditioner of this embodiment includes a load detecting unit 210 for detecting the indoor load, a control unit 200 for controlling the operation of the compressors 12 and 14 in accordance with the detected indoor load, a timer 220 for counting the driving start retarding time of the second compressor 14, and a driving unit 230 for driving the outdoor fan 32 and the linear expansion valve 40 in accordance with the control of the control unit 200.

The control unit 200 controls the operation of the outdoor fan 32 as the driving start retarding time passes and further controls the opening of the linear expansion valve 40.

The following will describe a control method of the air conditioner that is structured as describe above.

When the user operates the air conditioner, the indoor load is detected by the load detecting unit 210 and the compressors 12 and 14 are driven in accordance with the detected indoor load.

At this point, when the indoor load is relatively high, both of the first and second compressors 12 and 14 are driven, in the course of which, when the indoor load is reduced to a predetermined level, the driving of the second compressor 14 is stopped and the first compressor operated (S1).

When the indoor load increases again to satisfy the driving start condition of the second compressor (S2), the second compressor 14 is driven after a predetermined driving start retarding time, e.g., 10 minutes, has elapsed. At this point, the driving start retarding time is counted by the timer 220.

For example, when a first predetermined driving start retarding time, e.g., 8.5 minutes, has elapsed, the control unit 200 fully opens the linear expansion valve 40 for a first reference time, e.g., 15 seconds.

Then, since the flow rate of the refrigerant increases, the discharge temperature of the second compressor 14 is reduced and thus the discharge pressure of the second compressor 14 is reduced.

When the first reference time has elapsed, the control unit 200 returns the linear expansion valve to an initial state (S4).

Next, when a second predetermined driving start retarding time, e.g., 9 minutes, has further elapsed, the driving of the outdoor fan 32 is stopped for a second reference time, e.g., 10 seconds.

Then, the temperature of the refrigerant passing through the outdoor heat exchanger 30 increases and thus the condensing pressure increases. As a result, the intake pressure of the second compressor 14 increases.

When the second reference time has elapsed, the driving of the outdoor fan 32 is stopped (S6).

Subsequently, when the driving start retarding time has elapsed (S7), the second compressor 14 is driven (S8).

Therefore, the discharge pressure of the second compressor is forcedly reduced and the intake pressure of the second compressor forcedly increases. As a result, the difference between the discharge and intake pressures becomes less than a predetermined value. Therefore, when the driving start condition of the second compressor is satisfied, the second compressor can be driven immediately after the driving start retarding time has elapsed.

Here, in the present embodiment, the discharge pressure of the second compressor 14 is reduced before the intake pressure of the second compressor 14 increases. However, the present invention is not limited to this embodiment. For example, the intake pressure of the second compressor 14 is reduced before the discharge pressure of the second compressor 14 increases. 

1. A method of controlling an air conditioner, comprising: driving a first compressor among a plurality of compressors; determining if a driving start condition of the second compressor is satisfied during driving of the first compressor; and adjusting, when the driving start condition of the second compressor is satisfied, at least one of discharge and intake pressures of the second compressor for a driving start retarding time such that a difference between the discharge and intake pressures is less than a predetermined value.
 2. The method according to claim 1, wherein one of the first and second compressors is an inverter compressor and the other is a constant compressor.
 3. The method according to claim 1, wherein the driving start retarding time is a time measured after only the first compressor is driven.
 4. The method according to claim 1, wherein the discharge pressure of the second compressor is reduced for the driving start retarding time of the second compressor.
 5. The method according to claim 4, wherein a linear expansion valve is fully opened for a first reference time to reduce the discharge pressure of the second compressor.
 6. The method according to claim 5, wherein the opening of the linear expansion valve is returned to an initial state when the first reference time has been elapsed.
 7. The method according to claim 1, wherein the intake pressure increases for the driving start retarding time of the second compressor.
 8. The method according to claim 7, wherein an outdoor fan is stopped for a second reference time in order to increase the intake pressure of the second compressor.
 9. The method according to claim 8, wherein the outdoor fan starts operating after the second reference time has been elapsed.
 10. The method according to claim 1, wherein the discharge pressure of the second compressor is reduced for the driving start retarding time while the intake pressure of the second compressor increases for the driving start retarding time.
 11. The method according to claim 10, wherein the reduction of the discharge pressure and the increase of the intake pressure are sequentially realized.
 12. The method according to claim 11, wherein a linear expansion valve for adjusting a flow rate of the refrigerant is fully opened for a first reference time to reduce the discharge pressure of the second compressor and an outdoor fan is stopped for a second reference time in order to increase the intake pressure of the second compressor.
 13. The air conditioner according to claim 12, further comprising driving the second compressor after the driving start retarding time has been elapsed.
 14. A method of controlling an air conditioner, comprising: stopping driving of a first compressor during driving of a plurality of compressors; determining if a driving start condition of the first compressor is satisfied; and driving, when the driving start condition is satisfied, the first compressor after a driving start retarding condition has been elapsed, wherein a discharge pressure of the first compressor is forcedly reduced for the driving start retarding time or an intake pressure of the first compressor is forcedly increased for the driving start retarding time.
 15. The method of claim 14, wherein a linear expansion valve for adjusting a flow rate of the refrigerant is fully opened for a first reference time to reduce the discharge pressure of the second compressor.
 16. The method according to claim 15, wherein the opening of the linear expansion valve is returned to an initial state when the first reference time has been elapsed.
 17. The method according to claim 16, wherein driving of an outdoor fan is stopped for a second reference time after the opening of the linear expansion valve is returned to the initial state.
 18. The method according to claim 17, wherein the outdoor fan starts driving after the second reference time has been elapsed.
 19. An air conditioner comprising: first and second compressors; an outdoor heat exchanger through which refrigerant discharged from the first and second compressors passes; an outdoor fan for forcedly directing air toward the outdoor heat exchanger; an expansion valve for expanding the refrigerant discharged from the outdoor heat exchanger; an indoor heat exchanger through which the refrigerant expanded in the expansion valve passes; a linear expansion valve for adjust a flow rate of the refrigerant; a load detecting unit for deterring an indoor load; and a control unit for controlling the operation of the first and second compressors in accordance with the detected indoor load, wherein, in a state where the second compressor is not driven, the control unit allows the second compressor to drive when a driving start conditioner of the second compressor is satisfied and a driving start retarding time has been elapsed; and the control unit adjusts an opening of the linear expansion valve or an operation of the outdoor fan for the driving start retarding time.
 20. The air conditioner according to claim 19, wherein the linear expansion valve is fully opened for a first reference time within a range of the driving start retarding time and the outdoor fan is stopped for a second reference time within a range of the driving start retarding time. 